The new study looked hospitalization rates for serious injuries between 1997 and 2009, not just data from child protective services agencies.

Contrary to what was thought, cases of child abuse that cause serious injury or death may be on the rise, a new study finds.

The results show that between 1997 and 2009, hospitalizations for serious injuries caused by child abuse, such as fractures and traumatic brain injuries, increased by about 5 percent in the United States. Hospitalizations among children less than 1 year old increased 10.9 percent, the researchers said.

The findings are based on information from a U.S. national database of children's hospital records.

Earlier studies conducted using data from child protective services agencies presented a very different picture. Those studies showed a 55 percent decline in rates of child abuse over a similar time period.

Information from such agencies does not look at hospitalizations for injuries, but rather, it includes cases of validated physical abuse that occurred in the United States in a given year.

The decrease seen in studies that use data from agencies may be due to changes in reporting of cases to the agency, rather than a true decline in child abuse, the researchers said.

The findings from the new study "highlight the challenge of using a single source of data to track a complex problem such as child physical abuse," the researchers said.

The hospital data show that there was an increase in the percentage of children who died from abuse-related injuries, from 0.25 deaths per 100,000 children in 1997, to 0.36 deaths 100,000 children in 2009.

The average length of hospital stays for children with abusive injuries did not change over time, the study also found.

The findings underscore the need to develop prevention programs to reduce death and disability from child abuse. These programs should include strategies to help parents and caregivers respond in nonviolent ways to the stresses of caring for young children, the researchers said.